of Copper Sheeting by Sea-water, fyc. S3 



With zinc or iron, whether malleable or cast, no such di- 

 minution of effect was produced. The zinc occasioned only 

 a white cloud in the sea-water, which speedily sunk to the 

 bottom of the vessel in which the experiment was made. The 

 iron occasioned a deep orange precipitate : but after many 

 weeks, not the smallest portion of copper was found in the 

 water ; and so far from its surface being corroded, in many 

 parts there was a regeneration of zinc or of iron found upon it. 



6. In pursuing these researches, and applying them to 

 every possible form and connection of sheet copper, the results 

 were of the most satisfactory kind. A piece of zinc as large 

 as a pea, or the point of a small iron nail, were found fully 

 adequate to preserve forty or fifty square inches of copper ; 

 and this, wherever it was placed, whether at the top, bottom, 

 or in the middle of the sheet of copper, and whether the cop- 

 per was straight or bent, or made into coils. And where the 

 connection between different pieces of copper was completed 

 by wires, or thin filaments of the fortieth or fiftieth of an inch 

 in diameter, the effect was the same ; every side, every sur- 

 face, every particle of the copper remained bright, whilst the 

 iron or the zinc was slowly corroded. 



A piece of thick sheet copper, containing on both sides 

 about sixty square inches, was cut in such a manner as to 

 form seven divisions, connected only by the smallest filaments 

 that could be left, and a mass of zinc, of the fifth of an inch 

 in diameter, was soldered to the upper division. The whole 

 was plunged under sea- water; the copper remained perfectly 

 polished. The same experiment was made with iron: and 

 now, after a lapse of a month, in both instances, the copper is 

 as bright as when it was first introduced, whilst similar pieces 

 of copper, undefended, in the same sea-water, have undergone 

 considerable corrosion, and produced a large quantity of green 

 deposit in the bottom of the vessel. 



A piece of iron nail about an inch long was fastened by a 

 piece of copper wire, nearly a foot long, to a mass of sheet 

 copper, containing about forty square inches, and the whole 

 plunged below the surface of sea-water; it was found, after a 

 week, that the copper was defended by the iron in the same 

 manner as if it had been in immediate contact. 



A piece of copper and a piece of zinc soldered together at 

 one of their extremities, were made to form an arc in two dif- 

 ferent vessels of sea-water; and the two portions of water 

 were connected together by a small mass of tow moistened in 

 the same water : the effect of the preservation of the copper 

 took place in the same manner as if they had been in the same 

 vessel. 



Vol. 64. No. 315. July 1824. E As 



